This disclosure relates to a method of preparing a graphene shell and a graphene shell obtained using the method.
Generally, graphite exists in the form of stacked two-dimensional graphene sheets each made of hexagonally connected carbon atoms. Recent research has found that one or more graphene sheets ripped from graphite have very useful characteristics different from existing materials.
One of the recently discovered characteristics of the graphene sheets is very attractive in that electrons move in the graphene sheets as if they have no mass. This means that the electrons can move at the speed of light in a vacuum. Furthermore, the graphene sheets have an unusual electron-hole characteristic, that is, a half-integer quantum hall effect.
Currently known electron mobilities of graphene sheets range from about 20,000 cm2/Vs to 50,000 cm2/Vs. Carbon nanotubes are expensive due to poor purification yields even though they are synthesized using inexpensive materials. Thus, carbon nanotubes are not cost-competitive as compared with inexpensive graphite sheets. Single wall carbon nanotubes have metal characteristics or semiconductor characteristics depending on their chirality and diameter. In addition, although single wall carbon nanotubes have semiconductor characteristics, they have different energy band gaps. Therefore, for example, when only metallic single wall carbon nanotubes or only semiconductor single wall nanotubes are necessary, the metallic single wall carbon nanotubes or semiconductor single wall nanotubes should be separated from given single wall nanotubes. However, in practical terms, it is very difficult to separate single wall carbon nanotubes according to their characteristics.
However, the electrical characteristics of graphene sheets vary depending on the crystalline direction of a given thickness of graphene sheets, and thus can be controlled. Desired devices can be easily manufactured using the graphene sheets. These characteristics of the graphene sheets may be very useful for carbon-based electrical devices or carbon-based electromagnetic devices.
However, it is difficult to devise a cost effective and highly reproductive method of fabricating graphene sheets into three-dimensional structures. Currently known methods thereof include a micromechanical method and a SiC crystal thermal decomposition method.
In the micromechanical method, a sheet of tape such Scotch tape is attached to graphite, and then the tape is stripped off to obtain graphene sheets adhered to the tape. However, in this case, the number of graphene sheets is not predictable, and the shapes of the obtained graphene sheets are irregular like torn papers.
In the SiC crystal thermal decomposition method, a SiC single crystal is heated to disintegrate SiC of a surface layer, and thus removing Si. The remaining carbon (C) forms a graphene sheet. However, the SiC crystal thermal decomposition method is disadvantageous in that the SiC single crystal is very expensive, and it is difficult to fabricate a large graphene sheet. Furthermore, it is difficult to control the crystalline characteristics and three-dimensional shape of the graphene sheet.
Therefore, there is a need for a method of fabricating graphene sheets having good crystalline characteristics and a three-dimensional structure.